1. Field of the Invention
The present invention relates to a method of manufacturing an optical fiber cord comprising a plurality of tension fibers juxtaposed longitudinally along about an optical fiber ribbon and a sheath composed of a resin covering all the exteriors thereof.
2. Description of the Related Art
Known in the art is an optical fiber ribbon cord comprising a plurality of optical fibers bound in the shape of a tape and all the exteriors thereof are covered with a sheath in the shape of a rectangle or an oval, because of easy joining with a connector and the advantage of equalizing every transmission line length of optical fibers. FIG. 1A and FIG. 1B are the cross-sectional views of the conventional optical fiber ribbon cord at rest just as manufactured and of the optical fiber ribbon cord in operation, respectively. In FIG. 1A, the optical fiber ribbon cord 1 comprises a fiber ribbon 2 disposed in the center with multi-fibers (12 fibers), tension fibers 3 juxtaposed longitudinally (Z-direction) along about the fiber ribbon 2 in order to supply tensile strength, and a sheath 4 covering them.
The tension fibers 3 carry out the functions of a cushion for preventing external force from direct application via the sheath 4 onto the fiber ribbon 2, since the tension fibers 3 are located between the fiber ribbon 2 and the sheath 4.
However, in the conventional optical fiber ribbon cord 1, it is difficult to keep the tension fibers 3 staying stably in the direction of the major axis (X-direction) of the fiber ribbon 2 during operation, since the tension fibers are liable to move upward or downward in the direction of the minor axis (Y-direction) of the cord from the fiber ribbon 2 as a borderline, as shown in FIG. 1B.
Thus, when external force is applied from the direction of the major axis, the fiber ribbon 2 directly contacts the sheath 4 to generate large bending of fibers a, b, which are located at both ends of a plurality of fibers in the fiber ribbon 2, resulting in increase in attenuation or occasional interruption of signal transmission with breaking of the fibers.
In order to overcome such a situation, it was considered that the distance from the edge of the fiber ribbon to the fiber at the end would be longer, but there has still remained such a problem for practical use that enlargement of the tape width results in being mismatched with the size of a fiber ribbon insertion portion of a connector.
The present invention has been made in consideration of such circumstances, and according to the present invention provided are an optical fiber ribbon cord and a method of manufacturing the same, wherein enhancement of the transmission characteristics, especially, prevention of increase in attenuation at low temperature has been attempted by preventing external force from being applied directly to an optical fiber ribbon keeping the fiber ribbon from bending even when the external force is applied to a sheath.
According to a first technical aspect of the present invention, an optical fiber ribbon cord comprises a fiber ribbon including a plurality of optical fibers, the fiber ribbon having a cross-section which is flat in the first direction, a plurality of the first tendency providers juxtaposed along about the optical fiber ribbon, a sheath covering the exteriors of the fiber ribbon and the first tendency providers, and at least one second tendency provider inserted in the sheath, wherein the second tendency provider provides rigidity at least in the direction crossing the first direction.
According to a second technical aspect of the present invention, the second tendency provider is disposed by the side of an end portion in the first direction of the fiber ribbon.
According to a third technical aspect of the present invention, in the first technical aspect, the second tendency provider is a cushion member and disposed by the side of an end portion in the first direction of the fiber ribbon.
According to a fourth technical aspect of the present invention, in the first technical aspect, the first tendency providers adhere firmly to the interior of the sheath at least by the side of an end portion in the first direction of the fiber ribbon.
According to a fifth technical aspect of the present invention, in the first technical aspect, the optical fiber ribbon cord further comprises reinforcement tapes which are stuck together in order to surround the fiber ribbon.
According to a sixth technical aspect of the present invention, a method of manufacturing optical fiber ribbon cords comprises steps of introducing a optical fiber cord, including both a fiber ribbon with a cross-section flat in the first direction having a plurality of optical fibers and a plurality of first tendency providers juxtaposed along about the optical fiber ribbon, into an extruder; introducing at least one second tendency provider into the extruder so as to be juxtaposed along the optical fiber ribbon cord in the direction crossing the first direction; and extruding sheathing resin through the extruder, and coating the optical fiber ribbon cord and the first tendency providers with the sheathing resin.
According to a seventh technical aspect of the present invention, in the step of introducing the second tendency provider in the sixth technical aspect into the extruder, the second tendency provider is introduced into the extruder so as to be juxtaposed by the side of an end portion in the first direction of the fiber ribbon.
According to a eighth technical aspect of the present invention, a method of manufacturing optical fiber ribbon cords comprises a step of juxtaposing a plurality of first tendency providers along about a fiber ribbon which has a cross-section flat in the first direction and a plurality of optical fibers, and introducing them into an extruder; a step of juxtaposing at least one cushion member along the fiber ribbon and the first tendency providers to introduce them into the extruder; and a step of extruding sheathing resin through the extruder to thermally fusion-bond the fiber ribbon, the first tendency providers and the cushion member.
According to a ninth technical aspect of the present invention, a method of manufacturing optical fiber ribbon cords comprises a step of juxtaposing a plurality of first tendency providers along about an optical fiber ribbon which has a cross-section flat in the first direction and a plurality of optical fibers, the first tendency providers being disposed at least by the side of an end portion in the first direction of the fiber ribbon; s step of applying adhesive to portions, which will contact to the interior of a sheath, of the first tendency providers disposed by the side of the end portion in the first direction of the fiber ribbon; and a step of extrusion-coating the exteriors of the fiber ribbon and a plurality of the first tendency providers with sheathing resin.
According to a tenth technical aspect of the present invention, a method of manufacturing optical fiber ribbon cords comprises a step of sticking reinforcement tapes together in order to surround a fiber ribbon which has a cross-section flat in the first direction and a plurality of optical fibers; a step of juxtaposing a plurality of first tendency providers along about the fiber ribbon; and a step of extrusion-coating the exteriors of the fiber ribbon, the reinforcement tape and a plurality of the first tendency providers with sheathing resin.